In hospitals and care centres, overhead hoisting systems are used for transporting patients and occupants that are physically handicapped to some degree.
The hoisting systems include a rail system consisting or including of one or more rails mounted at the ceiling. A sling or carrying strap for a person is suspended from a trolley which can run in the rail system.
The rail system may e.g. include or consist of stationary rails that are fixed and mobile rails that are movable. In this way it is possible to move the trolley and thereby a person suspended in the hoisting system from a first stationary rail via one or more mobile rails to a second stationary rail. The mobile rail used for the transfer is placed such that it is aligned with the first stationary rail. The trolley can then pass beyond the free end of the first stationary rail and over on the mobile rail. The mobile rail with the trolley is then moved to a position where the mobile rail is aligned with the second stationary rail, after which the trolley can be transferred to the second stationary rail.
The above procedure implies that the rails of the rail system are to have free ends which the trolley can pass. A safety problem arises hereby, as it will be possible for the trolley inadvertently to pass beyond the free end of a rail which is not aligned with another rail, with the consequent risk of personal injury and material damage.
Therefore, it is necessary to prevent the passage of the trolley beyond the free end of a rail which is not aligned with another rail. This may, for example, be provided by inserting a physical barrier in the path of the trolley near the free end of the rail. In order to prevent the possibility of errors it is desirable that the barrier is inserted and removed automatically.
An example of such a system is known from WO 2013/122538 A1 which indicates an arrangement for secure transfer of a trolley from one suspended rail to another. The arrangement includes two locking elements, each disposed at the free end of two rails. The locking element includes a rod which is vertically displaceable in a guideway between an upper and a lower position. In the lower position, the rod has a part placed in the path of the trolley, whereas in the upper position, the rod is outside the path of the trolley. The rod includes a horizontal journal with a wheel facing the free end of the rail. The locking elements each include a curving track adapted to engage the wheel of the opposing locking element. The track is designed such that the rod is lifted to its upper position when the rails are aligned, whereas the rod is lowered to its lower rail when the rails are offset. The free end is hereby blocked when the rails are offset, and the trolley is thereby prevented from inadvertently passing the free end of the rails, whereas the blockage is removed when the rails are aligned, such that the trolley can be safely transferred from one rail to the other.
Furthermore, from GB 711857 A and GB 703061 A are known arrangements of the kind mentioned in the introduction. In these documents there is no explanation about limitation as to the number of movable parts in order to improve reliability. There is no indication either as to one track being used as one of the engagement means in connection with a fault in order to increase safety.